Fibrinogen Induces IL-8 Synthesis in Human Neutrophils Stimulated with Formyl-Methionyl-Leucyl-Phenylalanine or Leukotriene B4

Abstract

Human exudative neutrophils have greatly increased stores of the neutrophil chemoattractant IL-8 compared with peripheral blood cells, but the mechanism for the increase is not defined. In this report, we show that treatment of peripheral blood neutrophils with the chemotactic peptide fMLP or with leukotriene B4 or fibrinogen results in little increase in the production of IL-8 by peripheral blood neutrophils. However, a chemotactically active dose of fMLP (5 × 10−9 M) or leukotriene B4 (1 × 10−7 M) in the presence of a physiological concentration (2 mg/ml) of fibrinogen results in a receptor-mediated, pertussis toxin-sensitive, synergistic 30-fold increase in IL-8 synthesis. The levels of IL-8 attained are comparable to those observed in exudative cells. Higher concentrations of fMLP (1 × 10−7 M) are associated with reduced IL-8 protein synthesis without IL-8 degradation, indicating a sensitive regulatory mechanism for IL-8 production. Treatment of neutrophils with fibrinogen and fMLP resulted in minimal changes in the steady state levels of mRNA for macrophage inflammatory protein-1α and -1β and monocyte chemoattractant protein-1. In contrast, in the presence of fibrinogen, the steady-state level of neutrophil IL-8 mRNA increased 8-fold with 5 × 10−9 M fMLP but was not decreased with 1 × 10−7 M fMLP, suggesting that neutrophils are specifically adapted to modulate neutrophil IL-8 synthesis through transcriptional and posttranscriptional mechanisms. The data indicate that fibrinogen can function not only as a substrate in the clotting cascade, but also as an important effector during the evolution of the innate immune response.

Inhibition of Human Neutrophil IL-8 Production by Hydrogen Peroxide and Dysregulation in Chronic Granulomatous Disease

“…The prolonged rate of production of IL-8 in CGD neutrophils was associated with a 50% or greater increase in IL-8 protein in CGD neutrophils compared with normal neutrophils, confirming our previous report (19).…”

“…Previous observations of the effects of formyl peptide stimulation on peripheral blood neutrophils from normal subjects were confirmed using a chemotactic dose of fMLF (5 ϫ 10 Ϫ9 M) in vitro, resulting in an increase in neutrophil IL-8 production that was detected within 30 min and continued through 120 min (19) (Fig. 1, top).…”

Poly-γ-Glutamate Capsule-Degrading Enzyme Treatment Enhances Phagocytosis and Killing of EncapsulatedBacillus anthracis

“…CapD-mediated neutrophil killing appeared to be dependent on complement, as it was reduced when heat-inactivated serum was used, similar to what has long been reported for other bacteria (16,28,41), and complement was shown to be necessary for neutrophil killing of an unencapsulated B. anthracis strain (data not shown). This is consistent with a preliminary report noting less C3 binding to encapsulated than to unencapsulated B. anthracis as well as less killing by human FIG.…”

“…Human neutrophils were isolated from healthy, unvaccinated volunteers using Histopaque 1077 and 1119 gradients according to instructions provided by the manufacturer (Sigma-Aldrich, St. Louis, MO) or by Ficoll-Hypaque density gradient centrifugation followed by dextran sedimentation (28) and resuspended in DMEM at a concentration of 2 ϫ 10 7 /ml. Results were the same with neutrophils purified by either method.…”

Leukotrienes: Underappreciated Mediators of Innate Immune Responses

“…In addition to their direct actions on leukocyte effector functions discussed above, 5-LO metabolites also promote innate immune responses indirectly by stimulating the elaboration of other inflammatory mediators, such as cytokines and chemokines, which themselves activate leukocyte recruitment and antimicrobial mechanisms. Examples of this phenomenon include the ability of LTB 4 to induce lung generation of TNF-␣ (58), MCP-1 by monocytes (59), and IL-8 by neutrophils (60), and of cysLTs to stimulate production of IL-5, TNF-␣ and MIP-1 ␤ by mast cells (61).…”